The present invention generally relates to apparatus for gripping and cutting wood in the form of trees or poles, particularly relates to gripping and cutting apparatus for mounting on the end of a boom of a boom assembly, and specifically relates to gripping and cutting apparatus for mounting on the end of a fiberglass boom of a boom assembly.
In the utility industry, it is necessary to trim tree limbs which have a possibility of interference with utility lines. Typically, trimming is performed by a person located in a bucket hoisted adjacent to the tree limbs and using a severing means to trim the desired limbs. In order to trim such tree limbs, the operator in the bucket must get into close proximity with the utility lines, which presents electrocution risks in the case of high power lines. To reduce the risk of electrocution in the event of accidental contact with power lines, at least one of the booms of the boom assembly is formed of fiberglass which is a poor electrical conductor compared to metal but which has a reduced load carrying capability than booms formed of metal. In addition, the limbs are often not in a position to be dropped to the ground after severance because of interference with the lines. Especially for bucket trucks having fiberglass booms having limited load carrying capabilities, as the operator""s weight is carried by the fiberglass boom, the operator is not allowed to rest or otherwise support the severed limb on the bucket as the boom assembly is not designed for this type of load. Thus, the operator often has to tie off the limb to a higher limb using a series of ropes and to then lower the limb to the ground. This is a time-consuming process and puts the operator in danger around power lines.
Boom carried tree pruning apparatus are known in the art, but mostly in the commercial tree growing industry and not in the utility industries. In particular, most prior, commercially available tree pruning apparatus are of a size and weight required to be carried by massive boom assemblies and vehicles and in particular are not of a design capable of being attached to and/or carried by boom assemblies formed of fiberglass. Thus, the expense of and limited versatility of the vehicles and boom assemblies prevented the market acceptance of such apparatus in the utility industries. Further, because of their relatively large mass and/or their inability to be attached to fiberglass booms, prior tree pruning apparatus were attached on metal boom assemblies which are electrically conductive. This significantly increased the risk of electrocution of the operator and people nearby. Furthermore, the controls for the boom carried tree pruning apparatus were mounted to the vehicle such that the operator often created an electrical path to ground which increased the risk of electrocution. Also, as tree limbs are at varying angles, viewing movement and operation of the boom carried tree pruning apparatus was often obstructed to the operator of the controls. Additionally, although many attempts have been made to solve the need for tree pruning apparatus for the utility industries, such prior attempts have suffered from various deficiencies which are believed to have prevented their market viability.
Thus, a need continues to exist for apparatus for gripping and cutting wood which is advantageous, especially when used in the utilities industries, and which overcomes the deficiencies and shortcomings of prior apparatus.
The present invention solves this need and other problems in the field of gripping and cutting apparatus by providing, in the preferred form, a gripping assembly including an extendable actuator having opposite ends pivotally mounted to crank arms extending radially from first and second shafts each having at least one gripping arm extending radially therefrom. The travel of the crank arms is limited by abutting with an abutment so that movement of the gripping arms is centered on the gripping head.
In other aspects of the present invention, the opposite ends of an extendable actuator are pivotably mounted to actuator ears within a tubular insert and to actuator ears of a mount pivotally mounted to the tubular insert, with the tubular insert being glued or similarly adhered within the tubular boom of a boom assembly. Thus, the insert provides a rigid mounting surface for the actuator when utilized for booms formed of fiberglass or other material which provides an inadequate medium for mounting the actuator as well as provides a cleaner, more compact package having a reduced tendency to catch on tree limbs, utility wires, and the like.
In further aspects of the present invention, the gripping and cutting assembly is mounted to the free end of a boom of a boom assembly for pivotable movement about a first axis, a second axis substantially perpendicular to the first axis, and a third axis substantially perpendicular to the first and second axes. In most preferred aspects of the present invention, the gripping and cutting assembly is rotated by a first rotary actuator received between the end plates of a U-shaped leveler mount and by a second rotary actuator mounted between the central plate of the U-shaped leveler mount and a head mount, with the gripping and cutting assembly being rotatable 360xc2x0 about the second rotary actuator.
In still further aspects of the present invention, the operation of a gripping and cutting apparatus mounted to a boom assembly is controlled utilizing a remotely operated control unit which is not connected to the vehicle to which the boom assembly is mounted in a manner which creates an electrical path and in the most preferred form is untethered to maximize the possibilities of potential operator positions and to minimize the risk of electrocution.
In additional aspects of the present invention, operation of the boom assembly is prevented when the saw bar is not in a home position and is thus most prone to damage. In the most preferred form of the present invention, a proximity switch on the cutting apparatus actuates a transmitter which provides an electromagnetic signal to a receiver at the base of the boom assembly for interlocking valve actuation of the boom assembly when the saw bar is not in its home position.
It is thus an object of the present invention to provide a novel apparatus for gripping and cutting wood.
It is further an object of the present invention to provide such a novel gripping and cutting apparatus especially adapted for fiberglass boom assemblies.
It is further an object of the present invention to provide such a novel gripping and cutting apparatus including an insert for receipt within a tubular boom and for providing an inside rigid mounting surface for an extendable actuator.
It is further an object of the present invention to provide such a novel gripping and cutting apparatus which does not create an electrical path to the remote control unit.
It is further an object of the present invention to provide such a novel gripping and cutting apparatus including an untethered remote control unit.
It is further an object of the present invention to provide such a novel gripping and cutting apparatus including a mechanical abutment to center the travel of the gripping arms in a gripping head.
It is further an object of the present invention to provide such a novel gripping and cutting apparatus providing pivotal movement of the gripping head about three perpendicular pivotable movement axes.
It is further an object of the present invention to provide such a novel gripping and cutting apparatus which locks out boom operation when the saw bar is not in its home position.
These and further objects and advantages of the present invention will become clearer in light of the following detailed description of an illustrative embodiment of this invention described in connection with the drawings.